Apparatus for making an electrode to be applied to the skin

ABSTRACT

A process and device for making an electrode to be applied to the skin in which a carrier provided with an opening is stuck, on the side remote from the skin, to a tag portion which covers the opening. Adhesive is applied to the tag and/or the carrier only on a locally restricted partial region of their facing surfaces and the tag is adhesively secured to the carrier.

The invention concerns a process and an apparatus for the production ofan electrode for application to the skin, in which a carrier providedwith an opening is stuck, on the side remote from the skin, to a tagportion which covers over the opening.

Electrodes for application to the skin (for example ECG-electrodes etc),which have a carrier having a central opening which is covered over onthe top side thereof by a cover portion (a so-called tag portion) havealready long been known. Usually on the underside the carrier has askin-compatible adhesive which is self-adhesive and which is coveredover by a pull-off film or sheet for the purposes of transportation orstorage. After the pull-off film or sheet has been pulled off thecarrier can be stuck on to the skin of the patient. The tag portioncarries an electrical connection to permit the connection of anelectrode cable, wherein that outwardly disposed connection (contactregion) is electrically connected to the region of the opening of thecarrier, which represents the actual sensor region. For example a liquidelectrolyte gel in a sponge or a solid conductive gel is applied in thatsensor region in order to transmit the electrical currents between theskin and the actual sensor region. From there the currents then passthrough the tag portion or along the tag portion outwardly to thecontact region.

It is already known for the tag portion to be stuck fast on the carrierby means of an adhesive which is activatable (which is thereforeinitially non-adhesive). For example it is possible to use aheat-activatable adhesive. Particularly in the case of electrodes inwhich the contact region is arranged in laterally displaced relationshipwith the central sensor region on a free projection of the tag portion,there is the basic problem that on the one hand the tag portion isintended to adhere firmly and sealingly everywhere to the carrier, andthat on the other hand a good electrical connection is to be madebetween the sensor region and the laterally displaced contact regionthrough the tag portion or along same. In that respect it is always tobe borne in mind that electrodes of this kind are disposable articlesand should therefore be of a simple structure and thus inexpensive interms of production.

In order to satisfactorily solve those problems, the process accordingto the invention provides that adhesive is applied to the tag portionand/or the carrier only on a locally delimited portion of their mutuallyfacing surface and then the tag portion and the carrier are stucktogether.

There is thus in particular the possibility of applying the adhesiveonly in the region of overlap between the tag portion and the carrier,missing out that region of the tag portion which later comes to lie atthe opening of the carrier. Thus it is possible for example to use anelectrically conductive tag portion which in the region of the openingof the carrier forms a sensor region which is electrically connected toa laterally displaced contact region preferably provided on a projectionof the tag portion. In contrast to a known procedure which involvesapplying adhesive over the full surface area involved, the locallydelimited application of adhesive can prevent the tag portion also beingcovered over by adhesive in the region of the opening of the carrier.Rather, the sensor region remains free from adhesive and can thus easilycontact the skin of the patient, for example by way of a conductive gel.

In principle it would also be possible for the tag portion to be madefrom electrically insulating material and for an electrically conductiveconductor track in layer form to be applied thereto. In that embodimentthe electrically insulating tag portion could already be coated with anactivatable adhesive prior to the application of the conductor track, orit could consist in general of an adhesively activatable material (forexample a thermoplastic material). Such a tag portion can then be gluedon to the carrier by activation of the adhesive (for example by heatinga melt adhesive or by chemical activation of a chemically activatableadhesive or by UV-irradiation of an UV-activatable adhesive, in whichcase the conductor track which extends between the layer of adhesive andthe carrier ensures good electrical contact between the sensor region inthe region of the opening of the carrier and a laterally displacedcontact region for the connection of an electrode cable. With theprocess according to the invention it is now additionally possible foran adhesive to be applied in locally delimited manner in the region ofthe conductor track in order to ensure that a sealing closure effect isalso afforded in the region of the conductor track as between the tagportion and the carrier, whereby in particular a gel disposed in theregion of the opening of the carrier cannot escape laterally between thetag portion and the electrode under the conductor track.

Further advantages and details of the invention will be described morefully with reference to the following specific description.

FIG. 1 diagrammatically shows an apparatus according to the inventionfor carrying out an embodiment of the process according to theinvention,

FIG. 2 is a view in section of an electrode produced by the processaccording to the invention or with an apparatus according to theinvention,

FIG. 3 shows the underside of a tag portion which can be used inconnection with the process or the apparatus according to the invention,and

FIG. 4 shows a further embodiment of an apparatus according to theinvention for the production of an electrode which can be stuck on tothe skin.

In the embodiment illustrated in FIG. 1 a web of carriers 1 is moved inthe direction of the arrow 2. The individual electrodes are then laterformed from that web in per se known manner along the separation lines 3or by being stamped out. Initially however the web is a continuous webwhich can be easily moved by way of per se known transport apparatuseswhich are therefore not shown.

The aim of the process according to the invention is to stick a tagportion 4 on to each carrier 1, more specifically above an opening 1a inthe carrier 1, which for example can be previously stamped out in astamping procedure (not shown). Finally, at its underside, in the regionof its opening la of the carrier 1 the tag portion 4 is to form anelectrical sensor region 4a which is electrically connected to thelaterally displaced contact region 4b for the connection of an electrodecable. At the same time the tag portion 4 is to be firmly and sealinglyconnected to the carrier 1.

For that purpose the embodiment of FIG. 1 has an electrically conductivetag portion 4 and, in accordance with the basic idea of the invention,the adhesive 5 is applied to the carrier 1 only in a locally delimitedportion. In the illustrated embodiment the application of adhesive is inan annular configuration around the opening 1a, that is to say only on apart of the region of overlap between the tag portion 4 and thecarrier 1. That annular application of adhesive provides for sealingintegrity as between the tag portion 4 and the carrier 1, around theopening 1a.

In principle the locally delimited application of adhesive could alsooccur on the underside of the tag portions 4. In this respect however anessential consideration is that the electrically conductive underside ofthe tag portion is not covered over by adhesive in that region whichlater comes to lie in the region of the opening 1a of the carrier 1,because otherwise the electrical contact between the sensor region ofthe tag portion and the skin would be interrupted.

To provide for the locally delimited application of adhesive, theembodiment of FIG. 1 has a plurality of nozzles 7 which are controlledin respect of their period of opening and past which the carrier web ismoved. In the illustrated embodiment the nozzles are arranged in twofixed, mutually displaced rows of nozzles which are arrangedtransversely to the direction of movement 2 of the carrier web. Theprogrammable electronic control unit 8 controls the period of openingand the time of opening of the nozzles of the adhesive applicator device10, by way of a control bus. When the speed of movement of the web ofcarriers 1 is known, by suitable matching of the opening time and theperiod of opening of the nozzles, it is possible by means of the nozzlesto apply precise, locally delimited adhesive patterns to the carriers,for example in the present case an application of adhesive which extendsaround the opening 1a in an annular configuration. In that respect theindividual spots of adhesive can be so closely adjacent that they mergetogether and overall afford a closed ring of adhesive (portion 6). Thetag portion 4 which is supplied for example from the side is then stuckon to that portion 6 and pressed firmly thereon. Thereupon theindividual carriers 1 can be cut or stamped out of the carrier web toform the individual electrodes.

The nozzles may also be disposed diagonally with respect to thedirection of travel. With the same distances between the nozzles, adiagonal arrangement provides that the droplets of adhesive fromadjacent nozzles are closer to each other.

In the process according to the invention the application of adhesiveoccurs in the production installation itself (and therefore `in line`),more specifically as closely as possible prior to the making of theconnection between the tag portions 4 and the carriers 1. In that way itis also possible to apply permanently active adhesives. In principlehowever it is also possible to apply adhesives which are not permanentlyactive, that is to say activatable adhesives, such as for example meltadhesives.

FIG. 2 shows an embodiment of an electrode which is produced with theprocess according to the invention. In per se known manner, on itsunderside, the carrier 1 has a self-adhesive, skin-compatible layer 14which is covered over by a cover film or sheet 15 for transportation andstorage purposes. The cover film 15 also covers over an electricallyconducting gel 13 provided in the region of the opening 1a of thecarrier 1. A tag portion 4 is glued fast on to the carrier 1 on the topside by means of locally applied adhesive. The tag portion 4 compriseselectrically conductive material. In relation to the central sensorregion 4a which is in contact with the skin by way of the gel 13 the tagportion 4 has a laterally displaced, freely projecting projection(tongue 4b), to which an electrode cable 12 can be connected for exampleby way of a crocodile clip 11.

As already mentioned the tag portion 4 may be entirely of electricallyconductive material, in which respect not only metals but alsoelectrically conductive plastic materials or for example carbon fall tobe considered. It is however also possible for the tag portion 4 tocomprise an electrically insulating material and to be provided, forexample coated, with conductive material on the whole of the undersidewhich is towards the carrier 1. At any event the locally delimitedapplication of adhesive prevents the sensor region 4a from being coveredover by adhesive and thus losing its conductivity towards the skin.

FIG. 3 shows a further embodiment of a tag portion which is connected toa carrier by means of the process according to the invention. FIG. 3 isa view on to the underside of the tag portion, that is to say that sidewhich then comes to lie on the top side of the carrier. An activatable,for example heat-activatable adhesive layer is initially providedentirely on that underside of the tag portion 4.

Printed on to that adhesive layer is an electrical conductor track 16 inlayer form, which constitutes on the one hand a sensor region 4a and onthe other hand a contact region 4b. After the tag portion has been puton to the carrier, it can be stuck to the carrier for example by theapplication of heat. In that operation however no glueing effect wouldoccur in the region of the conductor track 16. In order here nonethelessto achieve a glueing effect it is possible for an adhesive additionallyto be locally applied in the closely delimited portion 6', and thatadhesive seals off the conductor track 16 towards the carrier.

FIG. 4 shows an embodiment of an apparatus according to the inventionwhich, instead of nozzles, has a pad-type printing unit 17 in order tostamp adhesive 5 on to the web of the carriers 1 on locally delimitedregions. Both the web of the carriers 1 and the web of the tag portions4 are driven by way of transport devices 18 which are known per se. Tagportions 4 and carriers 1 are brought together in a joining station 19downstream of the adhesive-applicator unit 17. The tag portions can thenbe stamped or cut out of the web. A screen printing unit is also noted.

What is claimed is:
 1. An apparatus for producing adhesive electrodesfor application to the skin, each electrode being provided with acarrier having a side near the skin and a side remote from the skin andan opening and with at least a partially electrically conductive tagglued to the carrier on the side remote from the skin, and wherein saidtag covers said opening; the apparatus comprising;a device fortransporting carriers, a device for transporting tags, an adhesiveapplication unit for applying an adhesive in a locally delimited regionto the carriers or tags, a joining station downstream of the adhesiveapplication unit for joining and gluing together the carriers and tagssothat an electrically conductive area of each tag located in the regionof the opening in each carrier remains free of adhesive.
 2. TheApparatus of claim 1 wherein the adhesive applicator unit comprises aplurality of stationary nozzles which are controlled in respect to theirperiod of opening and by way of which adhesive can be locallyspecifically applied to the moving carrier tag portions.
 3. TheApparatus of claim 2 wherein the adhesive applicator unit comprises aprinting unit for locally applying the adhesive.